. Elementary text-book of zoology. Zoology. ELECTRICAL ORGANS. 141 the branchial pouches and the anterior cartilages of the pectoral fins, and consist of a number of perpendicular columns enclosed by walls of connective tissue. The columns are divided by a great number of membranous transverse partitions into a series of com- partments placed one above another. Each of the latter contains a layer of gelatinous tissue, and a finely granular plate containing nerve endings and large nuclei (electrical plate). The latter corre- sponds in a certain degree to the copper and zinc elements of the Volt
. Elementary text-book of zoology. Zoology. ELECTRICAL ORGANS. 141 the branchial pouches and the anterior cartilages of the pectoral fins, and consist of a number of perpendicular columns enclosed by walls of connective tissue. The columns are divided by a great number of membranous transverse partitions into a series of com- partments placed one above another. Each of the latter contains a layer of gelatinous tissue, and a finely granular plate containing nerve endings and large nuclei (electrical plate). The latter corre- sponds in a certain degree to the copper and zinc elements of the Voltaic pile, the former to the moist intermediate layers; while the connective tissue framework seems to serve only to carry the nerves and blood-vessels. Each transverse partition contains a rich network of nerves, which is distributed on the electrical plates. The face on which the nerves ramify is the same in all the columns of the same. FIG. 591.—Alimentary canal and generative organs of Clupea Harengus (at'cer Brandt). Si; gills; Oe, cesophagus; T", stomach ; Ap, pyloric appendages; D, intestine ; A, anus ; Vn, swimming bladder; Dp, pneumatic duct; S, spleen; T, testis; I'd,vas (leferens; Gp, genital pore. organ, and is always electro-negative, the opposite free surface being positive. In Malapterurus, the other surface of the plate (the posterior surface) on which the nerves enter is electro-positive, but this apparent exception is explained by the fact that the nerves pass through the plate and are distributed on the anterior surface, which is electro-negative. In the electric Eel (Gymnotus electricus] the electric organ lies at the side of the tail and consists of long horizon- tal columns; in Malapterurus it lies along the body beneath the skin. Similar organs in Mormyrus are distinguished as pseudelectric organs, since although they have a similar structure, they give rise to no electric phenomena. The digestive organs vary much in structure. The mouth, which is p
Size: 2665px × 938px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
